As part of the process of drilling wells in the earth, joints of pipe called “casing” are joined and placed in a hole drilled to a first intermediate depth to form a casing “string”. Cement is pumped between the casing string and the wall of the hole to mechanically hold the casing in place and prevent flow outside the casing. The well has been drilled deeper through the string of casing. Before drilling begins through the casing, blowout preventers are attached to the top of the casing. The purpose of the blowout preventer is to seal the top of the casing should excess pressure be encountered when drilling the well deeper.
Blowout preventers are often referred to in the oil and gas industry as “BOPs”. The blowout preventers are used to prevent blowouts during the drilling and production of oil and gas wells. The blowout preventer is installed at the well head for the purpose of preventing the escape of pressure in an annular space between the casing and drill pipe, or in an open hole during drilling and completion operations. During the drilling operation from a drilling platform, the blowout preventer is located some distance below the drilling rig floor. The drilling platform may include a rotary table or a top drive which is mounted within a circular opening in the floor. The rotary table is used to turn the drill string and support the drilling sting assembly. The blowout preventer is mounted on top of the well casing through which the drill string passes. These blowout preventers are massive structures, often weighing an excess of 35 tons in some drilling operations. The blowout preventers extend from the top of the casing to within a short distance of the bottom of the drilling platform.
It is common practice in the industry today for the large individual components of the BOP stack to be transported individually to the drilling site and erected under the drilling structure. This assembly operation usually requires laborers to work in very close contact with these large components within a limited space under the drilling structure. Additionally, with the limited working height and space under the drilling structure, the laborer normally has few lifting devices that can fit into this space to assist in this operation. The “stacking” of these large components normally requires one or more of the laborers to work under these large pieces while they are suspended overhead. Once the BOP stack is in place, the equipment must be pressure tested to check its ability to perform during the drilling operations. If any one of the components fails to test properly, the assembly process may have to be repeated to repair or replace the faulty component. This enhances the risks to personnel and the time required to bring the drilling rig to an operational state. Injuries ranging from the incidental to the serious have been experienced industry-wide due to this operation.
Additionally, during the well drilling, the BOP stack may be raised and lowered to gain the access required to install or remove well components that are located under the BOP stack. Again, this requires personnel to work in a limited space under a large suspended load with the minimal amount of lifting devices available to work properly in this limited space. These operations are especially dangerous since the removal and placement of well components under the BOP stack normally takes place at or below ground level leaving little or no escape from falling components.
During all the “stacking” and component installation process, alignment of components is a critical factor. Virtually all these components are assembled with the use of flanges. This requires that proper alignment must exist between the mating pieces to be able to install gaskets, seals and the bolting required for holding the components together. This requirement is not trivial since the lack of ability to maneuver heavy flanges, one relative to the other, greatly increases the difficulty of installation in a safe and proper manner.
Another concern affecting the BOP “stacking” operation is the lack of preventive maintenance performed on the lifting equipment. The lack of preventive maintenance can lead to the risk of failure of these devices. Since most of these lifting devices reside high off the ground and out of reach, regular maintenance is difficult to perform. This scenario is especially dangerous for the most common lifting devices where wire ropes or chains are the primary lifting means. Left unattended, these components can become prone to failure due to exposure to the inherently corrosive environment in and around the well area.
Since the BOP stack is one of the single most important pieces of safety equipment involved in the drilling operations, its functionality is essential and the time required to ensure this functionality is unavoidable. Given the current industry practice of BOP stack assembly, this time can become a critical path task in trying to prepare a drilling rig for operation. Any additional time required to bring a drilling rig up to its operational state obviously has negative economic consequences.
In the past, various U.S. patents have issued with respect to blowout preventer handling devices. U.S. Pat. No. 3,498,375, issued on Mar. 3, 1970 to J. D. McEwen, teaches an oil well derrick substructure with a blowout preventer dolly. The blowout preventer dolly is mounted on the one side of the structural steel framework of the oil well derrick. The dolly can be moved to a central area after the rotary table support has been removed from the central area of the structural steel framework. The dolly will support a blowout preventer in a manner so as to move the blowout preventer across an upper part of the job structure into the space vacated by the rotary table support. The blowout preventer can be lifted from the dolly by the travelling block. The dolly can then be retracted back to its outer position and the blowout preventer lowered into position.
U.S. Pat. No. 4,007,782, issued on Feb. 15, 1977 to Nyboe et al., describes a parking device for containing a blowout preventer aboard a floating drilling station. The parking device includes a parking frame which is capable of holding the blowout preventer with its center of gravity lining above the point to which the blowout preventer is supported on the parking frame. The blowout preventer can be moved as a unit back and forth between a parked position and an installed position for utilization on the drilling station. A first drive mechanism is provided for raising and lowering the parking frame. A second drive mechanism is provided for moving the parking frame sideways.
U.S. Pat. No. 4,359,089, issued on Nov. 16, 1982 to Strate et al., teaches a carrier for an oil well blowout preventer. This carrier includes a skid defined by a pair of sides with cross bars extending therebetween. A carriage is slidably mounted on rollers on the skid for movement toward and away from the wellhead. A cradle is pivotally mounted on the carriage for carrying a blowout preventer in a horizontal position and for movement from such horizontal position to a vertical position. Hydraulic cylinders are provided for moving the carriage along the skid, for moving a carriage transversely to align the blowout preventer with the wellhead, for moving the cradle from a horizontal to an erect position, and for moving the blowout preventer and a slide portion of the cradle vertically into and out of engagement with a well casing.
U.S. Pat. No. 5,121,1993, issued on Jun. 16, 1992 to Bush et al., describes capping equipment for blowout wells. This capping equipment includes a blocking system for blocking of the well, an anchorage system to support the blocking system, and a movable and inclinable support and positioning system. The positioning system includes a sliding ramp and mechanism for moving the blocking system to bring it above and into the casing to be blocked off.
U.S. Pat. No. 5,816,565, issued on Oct. 6, 1998 to M. H. McGufin, teaches a hydraulic blowout preventer lifter. This lifting apparatus includes a frame assembly having a pair of side beams spaced parallel to one another. A sliding sheave assembly is mounted on the frame assembly. The sliding sheave assembly has a first shaft with a plurality of sheaves mounted thereto and a second shaft with a plurality of second sheaves mounted thereto. A cylinder has a first end connected to the frame assembly and a rod end attached to the sliding sheave assembly. The cylinder rod end is capable of moving longitudinally relative to the first end to thereby alter the distance between the shafts. A cable having first and second ends is attached to the frame assembly and is received by the sheaves. A portion of the cradle is received by a snatch block having a lifting hook for attaching to the blowout preventer. The blowout preventer is lifted by extending the rod end of the cylinder to increase the distance between the first and second shafts. U.S. Pat. No. 5,957,431, issued on Sep. 28, 1999 to E. Serda, Jr., teaches a similar blowout preventer lifting device.
U.S. Pat. No. 6,053,255, issued on Apr. 25, 2000 to J. A. Crain, describes an apparatus and method for lifting blowout preventers. A series of tables are connected to the drums of winches and can also be secured to the blowout preventer so as to provide a compact and safe technique for the lifting of the blowout preventer.
U.S. Pat. No. 6,276,450, issued on Aug. 21, 2001 to P. D. Seneviratne, describes an apparatus and method for the rapid replacement of upper blowout preventers. The system utilizes a hydraulic pressure booster to operate a pipe handling/torque wrench. An air amplifier is provided to increase the air pressure to a main shaft break of the top drive system in order to provide torque back-up. A rotary table back-up structure provides a torque back-off for removing the upper blowout preventer. A drive ring prevents relative rotation between the rotary table structure and the blowout preventer.
These prior art blowout preventers do provide techniques for manipulating the blowout preventer so as to bring the lower flange of the blowout preventer into proximity with the upper flange of the wellhead. Unfortunately these devices do not ultimately provide for “fine” adjustment of the blowout preventer with respect to this upper flange. For example, even when the lower flange is in proximity to the top flange of the wellhead, the planes of the facing surfaces can be so offset as to prevent the bolts from passing through the associated bolt holes. In other circumstances, the flange of the blowout preventer is rotationally offset from the flange of the wellhead so that the bolt holes are not axially aligned. In other circumstances, the flange of the blowout preventer will be offset, by a small distance, to the side of the flange of the wellhead. As a result, it is necessary for workers to position themselves in the cellar so as to further manupilate the blowout preventer and to provide this precise alignment. Additionally, none of these prior art devices can allow for the precise installation and manipulation of a spacer spool between the bottom flange of the blowout preventer and the upper flange of the wellhead.
It is an object of the present invention to provide a blowout preventer handling apparatus which enhances the ability to deliver an assembled and tested blowout preventer stack to a drilling site.
It is another object of the present invention to provide a blowout preventer handling apparatus and method which can be utilized with various types of drilling structures.
It is another object of the present invention to provide a blowout preventer handling apparatus and method that can lift a variety of types of stacked configurations of blowout preventers without modifications to the stacked components.
It is a further object of the present invention to provide a method and apparatus for blowout preventer handling which is safe and avoids the need for personnel to be directly under the blowout preventer stack.
It is still another object of the present invention to provide a method and apparatus for a blowout preventer handling which can precisely align the associated flanges of the wellhead and the blowout preventer without the need for manual manipulation.
It is a further object of the present invention to provide a blowout preventer handling method and apparatus which allows the blowout preventers stack pressure and function testing to occur on site.
It is an further object to provide a method and apparatus which allows for the loose alignment of the transport skid or handling mechanisms within the wellhead area while still achieving precise alignment of the connectors.
It is a further object of the present invention to provide a positive means of lifting the blowout preventer stack and wellhead components.
It is another object of the present invention to provide a blowout preventer method and apparatus which can deliver and remove wellhead components below the raised blowout preventer stack without the need for personnel to be positioned directly under the stack.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.